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Multiple Choice
Which molecule acts as the primary electron carrier during the light-dependent reactions of photosynthesis?
A
Coenzyme Q (ubiquinone)
B
Cytochrome c
C
FAD
D
NADP$^+$
Verified step by step guidance
1
Understand the context of the question: The light-dependent reactions of photosynthesis occur in the thylakoid membranes of chloroplasts, where light energy is converted into chemical energy. These reactions involve the transfer of electrons through a series of molecules.
Identify the role of electron carriers: Electron carriers are molecules that transport electrons during biochemical reactions. In photosynthesis, they play a crucial role in transferring electrons from water to the final electron acceptor, NADP$^+$.
Recall the specific electron carrier involved: During the light-dependent reactions, electrons are excited by light energy and passed through the electron transport chain. NADP$^+$ acts as the primary electron carrier, accepting electrons at the end of the chain to form NADPH.
Compare NADP$^+$ with other options: Coenzyme Q (ubiquinone) and Cytochrome c are electron carriers in cellular respiration, not photosynthesis. FAD (flavin adenine dinucleotide) is also involved in cellular respiration, specifically in the Krebs cycle and electron transport chain, but not in photosynthesis.
Conclude that NADP$^+$ is the correct answer: NADP$^+$ is specifically involved in photosynthesis as the final electron acceptor during the light-dependent reactions, forming NADPH, which is used in the Calvin cycle to synthesize glucose.